The human species began its ascent to becoming the dominant species on the surface of the earth in large part due to its development of agricultural technique. The ability to grow plants under controlled conditions and to domesticate animals allowed groups of humans to remain in a particular location for extended periods of time and to generate greater amounts of food than were necessary for immediate consumption.
A necessity for producing food under controlled conditions, particularly under adverse conditions, has remained a priority of the species since prehistoric times. Artificial growing environments, ranging from those found in ordinary greenhouses to those found in restricted circumstances such as caves, submarines and the like are utilized and are desirable for a variety of reasons. One of the primary reasons for controlled situs agriculture is to produce food for those who are cut off from ordinary sources of fresh produce. This is particularly important in the consideration of long term space voyages and permanent stations, in which the difficulties of transporting fresh produce to the inhabitants will be extremely high.
An important byproduct of the use of photosynthetic plants in a closed environment is that the plants recycle carbon dioxide generated in the breathing process of mammals, such as humans, and produce oxygen therefrom. For this purpose, as well, it is of significant importance for methods to be developed for efficiently growing photosynthetic plants in oxygen deprived circumstances.
A variety of prior art methods have attempted to grow plants of different types under controlled conditions. These have included a number of developments in the field of hydroponics and a large variety of efforts relating to the growth of algae and plankton. Some of these methods have been reflected in specific structures to be utilized for efficient growth of plants under limited and adverse conditions. One such is found in U.S. Pat. No. 4,932,158, issued to D. Roberts. This hydroponics structure facilitates a flow process growth system which is highly mechanized. Further, U.S. Pat. No. 4,780,989, issued to S. Mears, et al., demonstrates a further hydroponics system. A system which utilizes a gravity feed, and thus would be limited for gravity independent conditions such as might be present on a space station, is shown in U.S. Pat. No. 4,756,120, issued to J. Arledge. Each of these structures represents an advance in the art, but none solve all of the problems which are expected to be encountered in the limited space, recycled environment, growing conditions of the space station and the like.
One structure which has been developed specifically for utilization in gravity independent systems is illustrated in U.S. Pat. No. 3,882,634, issued to R. Dedolph. This structure utilizes a rotary method with multiple growing locations on each of a variety of vanes. The radially spaced vanes are rotated on a central structure and are provided with nutrient infusion by a controlled system. It is particularly noted that the Dedolph patent provides a detailed discussion of the mathematics and physics involved in the growth of plants under gravity independent conditions.
Plants which are grown under controlled conditions in environmental isolation are subject to limitation in receiving adequate supplies of four primary growth requirements. For most plants, and particularly for the "salad" type of plants, which are particularly desirable for consumption by humans under confined conditions, these requirements include light (electromagnetic radiation in the appropriate wavelengths for providing photosynthesis); carbon dioxide (ordinarily available through the ambient air); water and growth support nutrients. Beyond this, the plants must also have sufficient room to grow in a natural fashion and must have physical support.
One particular area in which a variety of techniques have been utilized is in the provision of light. It is well known among greenhouse operators that, for example, plant growth stimulation may be achieved by modifying the nature and duration of light which is provided to the plants. Further, the intensity and concentration of the electromagnetic energy is also important in achieving proper growth. For example, it has been found that direct radiation can be much less efficient in achieving significant and even growth in a wide variety of plants than is diffuse radiation.
One example of a patent on a structure which utilizes reflective techniques in order to provide the desired degree of electromagnetic radiation to a particular growing environment is shown and described in U.S. Pat. No. 5,095,414, issued to R. Tinus. This patent illustrates a method in which a parabolic reflector is utilized to sweep over an array of plants and to provide the necessary degree of illumination.
Despite many advances in the art and substantial efforts in a number of countries, there remains a great deal of room for improvement in providing methods for growing plants under confined and adverse conditions. In particular, the development of handy, energy efficient, space efficient and lightweight growing structures for use in the space program is particularly desirable. Since nothing has filled all of the requirements, to date, there remains substantial room in the field for new and innovative structures and techniques.